Variation & Natural Selection

9.New strains of the crop plant wheat can be produced by cross-breeding disease resistant plants with those that give high yields of grain. What is this an example of?

10.An island’s entire population of a species of butterfly are descended from just two parents introduced from the mainland. Which of the following statements about this species of butterfly, compared with that of the mainland, is correct?

11.A patient with a bacterial infection is treated with antibiotics, but some of the bacteria survive. Which statement is correct about the bacteria that have survived?

12.A cactus is a type of xerophyte. Cacti have fewer stomata than other plants. How is this an adaptation to survive in desert conditions?

13.The graph shows the distribution of height in a population of 1000 adults. Which type of variation is shown?

14.The table shows the urine concentration of four mammal species. Which species is best adapted to a desert environment?

15.A population of bacteria is exposed to an antibiotic. Most bacteria die, but a few survive and reproduce. Which statement explains this?

16.A farmer wants to produce a new variety of wheat that is both disease-resistant and high-yielding. Which process should he use?

17.Which of the following is an example of discontinuous variation?

18.A hydrophyte has large air spaces in its leaves. What is the function of these air spaces?

19.The graph shows the distribution of a characteristic in a population. Which characteristic is most likely to produce this graph?

20.In a population of snails, a mutation produces a white shell. The white snails are better camouflaged on light-coloured rocks and survive longer. What will happen over many generations?

21.Which of the following is an adaptive feature of a xerophyte?

22.A student measures the length of leaves from 50 oak trees. The results show a range from 5 cm to 12 cm. Which type of variation is this?

23.Barhee dates are amber-coloured, soft, high-yielding and small-to-medium sized. Thoory dates are straw-coloured, dry, medium-yielding and medium-to-large sized. A farmer wants a medium-sized, straw-coloured, soft date with high yield. Which two varieties should he cross?

24.Which of the following increases the rate of mutation?

25.A student investigates the variation in leaf length of a plant species. She measures the length of 100 leaves and plots a bar chart. The bars show a smooth bell-shaped curve. Which type of variation is shown?

26.In a population of bacteria, a mutation occurs that makes some bacteria resistant to an antibiotic. The antibiotic is applied, killing most bacteria. The resistant bacteria survive and reproduce. What is this process called?

27.A desert plant has thick leaves and a waxy cuticle. Scientists make three statements: 1. These features reduce water loss. 2. These features are inherited characteristics. 3. These features developed because the plant needed them. Which statements are correct?

28.Which of the following statements is a correct definition of 'adaptive features'?

29.The graph shows the distribution of blood groups in one area. This is an example of discontinuous variation. Which statement about discontinuous variation is correct?

30.Which type of variation is shown by human blood groups?

31.Xerophytes have an inverted stomatal opening rhythm. This means that during the day when the sun is at its peak, most stomata of xerophytes are closed. Which statement explains a disadvantage of this for the plant?

32.Which of the following is a source of genetic variation?

33.In the process of natural selection, which of the following is directly responsible for the increase in frequency of a beneficial allele?

34.Barhee dates are amber-coloured, soft, high-yielding and small-to-medium sized. Thoory dates are straw-coloured, dry, medium-yielding and medium-to-large sized. A farmer wants to produce a new variety of date that is medium-sized, straw-coloured, soft, and high-yielding. Which two varieties should the farmer cross?

35.The graph shows the distribution of a characteristic in a population. Which characteristic is most likely to produce this bell-shaped curve?

36.In a population of bacteria, a mutation occurs that makes some bacteria resistant to an antibiotic. The antibiotic is applied, killing most bacteria. The resistant bacteria survive and reproduce. What is this an example of?

37.Sickle cell anaemia is a genetic disorder that causes severe illness in homozygous individuals. In some human populations, being heterozygous can be beneficial. What could be the reason for this?

38.A population of 1000 bean plants shows a range of heights from 10 cm to 50 cm. The distribution is a smooth bell curve. Which type of variation does this represent?

39.The table shows the yield (kg per plant) of four wheat varieties grown in two different fields. Which variety is best adapted to both fields?

40.A student investigates the effect of light intensity on the rate of photosynthesis in a hydrophyte. She places a pondweed in a beaker of water and counts the number of bubbles released per minute at different distances from a lamp. Which variable should be kept constant in this experiment?

41.What is variation in biology?

42.Continuous variation is usually caused by genetic variation alone.

43.Which of the following are examples of discontinuous variation in humans? (Select all that apply)

44.Match each plant type with its adaptation.

45.Place the following events in the correct order to describe natural selection in a snail population where white shells become more common.

46.Which of the following can increase the rate of mutation?

47.Selective breeding is also known as artificial selection.

48.Match each type of variation with its correct description or example.

49.Which of the following are sources of genetic variation in a population? (Select all that apply)

50.In a population of bacteria, a mutation occurs that makes some bacteria resistant to an antibiotic. The antibiotic is applied, killing most bacteria. The resistant bacteria survive and reproduce. Over time, the population becomes mostly resistant. Which statement correctly describes this process?

51.Complete the sentence.

52.A gerbil in a desert produces urine with a concentration of 5400 milliosmoles/L. A beaver in fresh water produces urine with a concentration of 480 milliosmoles/L. How many times more concentrated is the gerbil's urine compared to the beaver's? Give your answer to one decimal place.

53.State the term used to describe the theory of natural selection put forward by Charles Darwin.

54.Complete the sentences about sources of genetic variation.

55.Complete the sentence about adaptive features.

56.Explain how the development of antibiotic resistance in bacteria is an example of natural selection.

57.A gerbil in a desert produces urine with a concentration of 5400 milliosmoles/L. A beaver in fresh water produces urine with a concentration of 480 milliosmoles/L. How many times more concentrated is the gerbil's urine compared to the beaver's? Give your answer to one decimal place.